Kenneth Thorpe has a cheery simulation in this month’s Health Affairs postulatingthat if we enroll 2.6 million Americans aged 60-64 in a nutrition training program (run by the YMCA) we could save $7 billion over their lifetimes.

The simulation is based on the National Diabetes Prevention Program.,a huge well-designed study that resulted in 7% body weight loss sustained over 2.8 years of followup and reduced the prevalence of diabetes among the participants from 58% (and by 71% in those over 60).The intervention cost $1340 per person

The savings are available over the beneficiaries’ lifetimes –which makes it hard to imagine what the denominator is, since we don't usually think of the average liability for a person’s Medicare costs at the moment she turns 65.

The intervention in the NDPP cost $1340 per person and involved individual training, while the intervention at the YMCAs cost $240 per person and used classroom education, which a smaller number of sessions.

The simulation assumes that this intervention could be scaled from 92 people to 2.6 million enrollees

The $7 billion assumes 70% of those who are eligible (at risk for diabetes) enroll.Enrolling this many people in a program would be a staggering feat.Weight Watchers enrolls 1.2 million members, and has 56,000 employees.

Here’s the real kicker.If we accept all of these assumptions, believe that the very small YMCA trial is adequate proof of concept, and enroll overweight people at risk for both diabetes and heart disease, this program would save $3.7 billion over 10 years, or $370 million per year.Medicare will spend $569 billion in 2012.

That means that this intervention would shave 0.06% off of total Medicare spending.

This program is probably a very good idea – and keeping people from getting diabetes (or delaying onset) could clearly save money and make peoples’ lives better.But let’s not congratulate ourselves for finding a solution to cost increases in Medicare without dealing with the tougher issues.